[MacPerl] one's complement sum

["John W." <johnw@imagelinc.com>]

Hello Mac-Perlers:

My question doesn't relate to MacPerl except that this is the
environment I'm working in.  So, I'm hoping for a little
leeway from everyone.

The following is an excerpt from RFC 791 - DARPA INTERNET
PROGRAM PROTOCOL SPECIFICATION:

"The checksum field is the 16 bit one's complement of the
one's complement sum of all the 16 bit words in the header.
For purposes of computing the checksum, the value of the
checksum field is zero."

Now I now what one's complement is, but what is the
one's complement sum part.  Would this be an end around
carry summation in order to end up with a 16bit value?

TIA

John Whelan
johnw@imagelinc.com